A block copolymer means a polymer formed by linear linkage of two or more different monomers. A block copolymer forms a specific nanostructure through annealing, wherein the size and morphology of the nanostructure vary with the type, molecular weight, molar ratio, annealing process, etc. of the block copolymer. Particularly, a block copolymer thin film means a thin film having a thickness of several nanometers to several hundreds of nanometers. In addition, when the orientation of the nanostructure of block copolymer is controlled in such a thin block copolymer film, the nanosturcture may be introduced to the next-generation nano-process through pattern transfer, or the like.
The orientation of block copolymer nanostructure is determined by various factors. In general, when the difference in interfacial energy of polymer blocks forming a block copolymer is large, the nanostructure is oriented generally in parallel with a substrate. However, it is required for the nanostructure to be oriented vertically in order to apply an ultramicro-pattern to metallization.
It is reported that a random copolymer, etc. having neutral interfacial energy is coated on the top or bottom in order to obtain a vertically oriented block copolymer nanostructure. According to the method reported to date, the vertical orientation method is limited to specific types of block copolymers. Moreover, a complicated process is required in order to realize vertical orientation, since a random polymer is synthesized and introduced to each of the top and bottom of a film all the time. Thus, there has been a significant limitation in practical application.
Meanwhile, plasma means a state of material separated into electrons, ions, or the like, under the application of energy to gas. Such plasma causes reactions, such as crosslinking and etching, in a material, and the reactions vary with the type of plasma gas. Plasma also generates ultraviolet rays and vacuum ultraviolet rays, can penetrate a polymer film to a depth of several hundreds of nanometers or more, and causes a chemical change to a relatively deep film.
Various reactive species formed from plasma may be controlled by using introduction of a material, such as glass, or a diaphragm. In addition, it is required to select reactive species in order to selectively modify the surface of a material. Reactive species from plasma generally include ions, radicals, electrons, ultraviolet rays, or the like. Ions, radicals and electrons cause chemical modification to a level of several nanometers from the surface, while ultraviolet rays cause chemical modification to a level of several hundreds of nanometers from the surface. Thus, it is required to inhibit ultraviolet rays selectively to carry out crosslinking on the surface of a block copolymer to a level of several nanometers.